A rainbow of color lit up wispy cirrus clouds high in the sky over Pinnacles National Park on Tuesday.The surreal-looking sight is what's known as "fire rainbow" or in more scientific terms, a circumhorizontal arc, and was caught on camera by a runner in the park who sent photos to the National Weather Service.The natural phenomenon occurs when the sun is situated high in the sky (higher than 58 degrees above the horizon) and its light is refracted by ice crystals suspended in the atmosphere, most commonly in cirrus clouds."When the sun hits the ice crystals, you get pretty colors," says Roger Gass, a meteorologist with the National Weather Service. "It's an optical illusion."The rarity of "fire rainbows" is dependent on the location of the observer. They're relatively common in the United States in the summer when the sun is situated high in the sky. They're extremely rare in Northern Europe.Matt Mehle with the National Weather Service Bay Area says he's only seen one in Yosemite National Park. Gass has never spotted one.

A rainbow of color lit up wispy cirrus clouds high in the sky over Pinnacles National Park on Tuesday.

The surreal-looking sight is what's known as "fire rainbow" or in more scientific terms, a circumhorizontal arc, and was caught on camera by a runner in the park who sent photos to the National Weather Service.

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The natural phenomenon occurs when the sun is situated high in the sky (higher than 58 degrees above the horizon) and its light is refracted by ice crystals suspended in the atmosphere, most commonly in cirrus clouds.

"When the sun hits the ice crystals, you get pretty colors," says Roger Gass, a meteorologist with the National Weather Service. "It's an optical illusion."

The rarity of "fire rainbows" is dependent on the location of the observer. They're relatively common in the United States in the summer when the sun is situated high in the sky. They're extremely rare in Northern Europe.

Matt Mehle with the National Weather Service Bay Area says he's only seen one in Yosemite National Park. Gass has never spotted one.